<table border="1" class="dataframe">
  <thead>
    <tr>
      <th></th>
      <th></th>
      <th colspan="3" halign="left">d</th>
    </tr>
    <tr>
      <th></th>
      <th>a</th>
      <th>aa</th>
      <th>...</th>
      <th>ac</th>
    </tr>
    <tr>
      <th>b</th>
      <th>c</th>
      <th></th>
      <th></th>
      <th></th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <th>ba</th>
      <th>ca</th>
      <td>1.0</td>
      <td>...</td>
      <td>NaN</td>
    </tr>
    <tr>
      <th>bb</th>
      <th>cb</th>
      <td>NaN</td>
      <td>...</td>
      <td>NaN</td>
    </tr>
    <tr>
      <th>bc</th>
      <th>cc</th>
      <td>NaN</td>
      <td>...</td>
      <td>3.0</td>
    </tr>
  </tbody>
</table>
